Politicians depend on their ability to maneuver as their most basic survival skill. Force them to stand and exchange blows without the ability to shift their ground and they are as helpless as a kitten.

Presidents fail as well when they get stuck and can no longer maneuver, as with Lyndon Johnson on Vietnam, Richard Nixon on Watergate, Jimmy Carter on the hostages in Iran, Ronald Reagan on Iran-Contra, George H.W. Bush on taxes, Bill Clinton on Monica Lewinsky and George W. Bush on Iraq.

Now, Hillary Clinton is stuck over her emails.

Her ability to maneuver on the issue is lost and comes down to a simple mantra: "I erased the emails. There's nothing there you wanted to see. Trust me."

Clinton's tactic of hiding at home in Chappaqua, N.Y., coming up occasionally to tweet, offering up to 140 characters to show she's still alive, isn't working. She is getting pounded each day in the media. Nobody believes her explanations.

About half the voters in the swing states of Ohio, Florida and Pennsylvania told Quinnipiac pollsters that they do not find the former secretary of State "honest and trustworthy." And a recent poll by CBS showed that while voters believed by 49 percent to 38 percent that "convenience" rather than "concealment" was her motive for using a private server, it does nothing to justify her erasure of 30,000 emails. For that, she has no explanation other than to repeat that the emails are none of our business.

Voters aren't buying that.

Under the constant attacks and disclosures, Clinton offers no defense  and not even any offense  against Republicans.

The bad polls and the nervousness of Democrats will combine to force the candidate-in-hiding to come out in public, announce her candidacy and campaign. While going public is the only real option for Clinton at this point, it will prove counterproductive and only mire her more deeply in the email mess.

Hillary Clinton is truly stuck. Nothing she says about any other topic will be covered and the chance for the media to question her will just expose her to more negative coverage about the emails. She has already shown her difficulty in handling questions without proper scripting. She has nowhere to turn, nowhere to hide.

The question looming over the presidential race is: How much can the Democratic Party take before it comes up with a default candidate? Will it get serious about finding an alternative or is the party willing to bet that the bleeding stanches and the wound heals?

The extent of the catastrophe should the scandal drag out and the negatives continue that would befall the party cannot be overstated. The elections of 1974, the post-Watergate wipeout of Republicans, will seem minor compared to what will happen to Democratic congressional candidates in 2016 if Clinton leads the party into disaster.

Democrats seem impervious to negatives about Clinton. Through thick and thin, they appear willing to stick with her. So let's rephrase the question and ask Democrats whether they think she can win with her current baggage. As the evidence mounts that she cannot and her delayed announcement of candidacy just pushes her lower and lower, likely they will come to their senses and look for an alternative before it is too late.

As congressional hearings come and Clinton looks worse and worse in the witness chair, it will likely dawn on even the most dedicated of the party faithful that the jig is up. Even if Democrats' own admiration for her is undimmed, the prospect of carrying Clinton into the election will appear increasingly daunting.

And Democrats have to win in order to survive. Politics, for them, is no spectator sport. It's their living, their entitlement checks, their government handouts. They cannot afford, literally, to lose.